The present invention relates to engine cooling systems, and more particularly, to an engine-cooling fan having improved airflow characteristics.
The use of fans to move air through heat exchangers is well known, for example in the field of air conditioning and the field of motor vehicle cooling. A fan for such an application may consist of a hub member and plural blade members, each blade member having a root portion and a tip portion, the root portions of each blade being secured to the hub portion such that the blades extend substantially radially of the hub portion. A blade tip support ring may link the blades near to, or more usually, at their tip portions.
Such a fan, which is often driven by an electric motor, or via a transmission from an associated engine, is usually disposed so that the fan radial plane extends parallel to a face portion of the associated heat exchanger.
Fans of this type are commonly referred to as xe2x80x9caxial flow fans.xe2x80x9d However, although the blades are pitched so as to move air in an axial direction, nevertheless the action of the fan causes a relatively complicated airflow. It will, for example, be apparent that rotation of the fan causes air that has passed through the fan to have a rotational component of motion, due to the movement of the blades, as well as a linear component induced by the pitch of the blades. Leakage of air around the fan blade tips (so-called tip vortices) between the high and low-pressure sides of the fan may also occur.
Furthermore, the particular blade form and the particular blade disposition selected for a fan, for example the dihedral angle of the blade, the variation in pitch along the blade span or the chord length of the blade (taken along a radial cross section) will affect the pressure distribution provided immediately adjacent the fan, and hence will affect the flow of air which has passed through the fan.
A fan of the type used to move air through a heat exchanger is intended to provide airflow in an axial direction; components in other directions are wasteful of energy. Such wasteful components of airflow impinge upon the various mechanical structures around the heat exchanger and upon the heat exchanger itself to increase the overall noise produced by the system.
It is accordingly an object of the present invention to at least partially mitigate the above-mentioned difficulties.
The above and other objects of the invention are met by the present invention, in which either a stator or a diffuser assembly is closely coupled with an engine mounted cooling fan.
Both the stator and diffuser assembly independently improve airflow efficiency, thereby reducing vibrational noise associated with inefficient airflow. The improved airflow also acts to increase the cooling capabilities of the fan, which can lead to improved engine fuel economy.
In addition, by mounting the stator or diffuser assembly to the engine, a tighter tip clearance to the blades of the fan can be achieved, which reduces airflow inefficiency and further leads to reduced noise levels and fuel efficiency.
Other features, benefits and advantages of the present invention will become apparent from the following description of the invention, when viewed in accordance with the attached drawings and appended claims.